Chemical composition and assessment of larvicidal and repellent capacity of 14 Lamiaceae essential oils against Aedes albopictus.

In the current laboratory study, 14 essential oils (EOs) derived from 12 Lamiaceae plant species and their major components were screened for their larvicidal and repellent properties against Aedes albopictus, an invasive mosquito species of great medical importance. The results of toxicity bioassays revealed that the EOs from Thymus vulgaris, Ocimum basilicum, Origanum dictamnus, Origanum majorana, and Origanum vulgare, as well as their major components (terpenes), namely thymol, carvacrol, p-cymene, and γ-terpinene exerted the highest larvicidal effect. Essential oils from Mellisa officinalis, Origanum dictamus, Mentha spicata (chem. piperitenone epoxide), Origanum majorana, and Satureja thymbra were the most potent repellents, with the last two assigned as the best ones. Among the terpenes tested, piperitenone epoxide, carvacrol, thymol, and piperitenone provided the highest level of protection against Ae. albopictus adults. Chemical analysis revealed the presence of a high number of terpenes in the EOs, while in most cases, the biological action of the tested EOs and their major components was in consistency. The most effective EOs and terpenes that were identified through the current laboratory bioassays could be used as alternative agents to control larvae and repel adults of Ae. albopictus.

Integrated analytical methodology to investigate bioactive compounds in Crocus sativus L. flowers.

INTRODUCTION: The increasing interest on Crocus sativus L. over the last decades is caused by its potential employment as a source of biologically active molecules, endowed with antioxidant and nutraceutical properties. These molecules are present mainly in stigmas and tepals, these last generally considered as byproducts. OBJECTIVE: To characterise bioactive compounds in stigmas, stamens, and tepals of Crocus sativus L. for quality, cross-contamination of tissues or fraudulent addition, joining spectroscopic and chromatographic techniques. METHODOLOGY: Fourier transform infrared (FT-IR) and Raman spectroscopies were initially employed, being very rapid in response; volatiles were more appropriately investigated by gas chromatography with mass spectrometry (GC-MS), while finally nuclear magnetic resonance (NMR) and high-performance liquid chromatography with a diode array detector (HPLC-DAD) were adopted for a more thorough characterisation of secondary metabolites. NMR was also used to investigate the anthocyanins content in tepals upon acid extraction. RESULTS: The results obtained highlighted the drying method as the dominant factor affecting the content of volatile constituents and contributing to the quality of saffron, while only slight differences were observed in the most abundant metabolites of stigmas, as well as in the anthocyanin content of tepals. In particular, for the first time, delphinidin and petunidin were detected by NMR in this latter tissue. CONCLUSION: The integrated analytical methodology here proposed, allowed to achieve a deeper level of compositional and structural details of secondary metabolites in Crocus sativus L. flowers.

Biocidal Compounds from Mentha sp. Essential Oils and Their Structure-Activity Relationships.

Essential oils from Greek Mentha species showed different chemical compositions for two populations of M. pulegium, characterized by piperitone and pulegone. Mentha spicata essential oil was characterized by endocyclic piperitenone epoxide, piperitone epoxide, and carvone. The bioactivities of these essential oils and their components have been tested against insect pests (Leptinotarsa decemlineata, Spodoptera littoralis and Myzus persicae), root-knot nematodes (Meloydogine javanica) and plants (Lactuca sativa, Lolium perenne, Solanum lycopersicum). The structure-activity relationships of these compounds have been studied including semi-synthetic endocyclic trans-carvone epoxide, exocyclic carvone epoxide, a new exocyclic piperitenone epoxide and trans-pulegone epoxide. Leptinotarsa decemlineata feeding was affected by piperitenone and piperitone epoxide. Spodoptera littoralis was affected by piperitone epoxide and pulegone. The strongest nematicidal agent was piperitenone epoxide, followed by piperitone epoxide, piperitenone and carvone. Germination of S. lycopersicum and L. perenne was significantly affected by piperitenone epoxide. This compound and carvone epoxide inhibited L. perenne root and leaf growth. Piperitenone epoxide also inhibited the root growth of S. lycopersicum. The presence of a C(1) epoxide resulted in strong antifeedant, nematicidal and phytotoxic compounds regardless of the C(4) substituent. New natural crop protectants could be developed through appropriate structural modifications in the p-menthane skeleton.

Evaluation of bioefficacy of three Citrus essential oils against the dengue vector Aedes albopictus (Diptera: Culicidae) in correlation to their components enantiomeric distribution.

Laboratory experiments were conducted to study the bioefficacy against Ae. albopictus of three Citrus essential oils, derived from peels of Citrus sinensis, Citrus limon, and Citrus paradise and of their components. Chiral gas chromatography analysis revealed the dominant occurrence of R-(+)-limonene and (-)-ß-pinene in all three essential oils while in the case of lemon oil γ-terpinene, neral, and geranial detected also among other components. The tested Citrus essential oils were toxic against mosquito larvae with LC(50) values ranging from 25.03 to 37.03 mg l(-1). Among citrus essential oils components tested, γ-terpinene was the most toxic (LC(50) = 20.21 mg l(-1)) followed by both enantiomeric forms of limonene (LC(50) = 35.99 and 34.89 mg l(-1), for R-(+)-limonene and S-(-)-limonene, respectively). The delayed toxic effects after exposure of larvae to sublethal (LC(50)) doses were also investigated for citrus essential oils and their major component R-(+)-limonene, indicating a significant reduction of pupal survival. In repellent bioassays, lemon essential oil, S-(-)-limonene, citral (mixture of neral\geranial) and (+)-ß-pinene were the most effective compared with other citrus essential oils and components against adult mosquitoes. Repellent bioassays also revealed that limonenes and ß-pinenes showed an isomer dependence repellent activity. Finally, according to enantiomeric distribution of limonene and α- and ß-pinene, the repellency of lemon essential oil is possibly attributed to the presence of citral.

Classification of Greek Mentha pulegium L. (Pennyroyal) samples, according to geographical location by Fourier transform infrared spectroscopy.

INTRODUCTION: Mentha pulegium L. (pennyroyal) is one of the four most commercially important Mentha species, even it is not a cultivated plant. It can be abundantly located in the Iberian Peninsula and North African countries. In Greece it grows in the wild and it is scattered all over the country. Pennyroyal is best known for its essential oil, with Spain and Morocco being the largest producers in the world. Mid-infrared spectroscopy has been applied to determine the origin of various samples. OBJECTIVES: In this work Fourier transform infrared spectroscopy (FT-IR) combined with canonical discriminant analysis has been applied to distinguish 70 Greek pennyroyal samples according to their collection areas. MATERIAL AND METHODS: Pennyroyal nonpolar organic extracts were prepared using ultrasound-assisted solvent extraction. The spectra of the extracts were recorded in the range of 4000-400 cm(-1) and the best discrimination was achieved in the spectral region 1720-1650 cm(-1) . RESULTS: Spectral features for the discrimination of pennyroyal samples among the different collection areas occur primarily in the carbonyl region and are correlated with the main volatile constituents of the extracts (menthone, isomenthone, pulegone, piperitone). All areas were easily differentiated by canonical discriminant analysis. The percentages of correct classification and validation were 94.3 and 90.0%, respectively. CONCLUSION: The combination of FT-IR spectroscopy and multivariate analysis provides a rapid and ambient method to discriminate pennyroyal samples in terms of geographical origin.

Saffron for "toning down" COVID-19-related cytokine storm: Hype or hope? A mini-review of current evidence.

AIM: To assess the potential role of saffron in downregulating inflammation and cytokine storm during COVID-19. MAIN FINDINGS: Three main compounds of saffron, i.e., crocetin esters, picrocrocin, and safranal, present strong antioxidant and anti-inflammatory action for several disease states (e.g., Alzheimer's, cancer, and depression) but have also been studied in COVID-19. In particular, based on our comprehensive review of both in vitro and in silico studies, saffron's essential oils and other constituents appear to have both immunomodulatory and anti-asthmatic actions; these actions can be particularly helpful to treat patients with respiratory symptoms due to COVID-19. Moreover, crocin appears to reduce the COVID-19-related cytokine cascade and downregulate angiotensin-converting enzyme 2 (ACE2) gene expression. Last, in silico studies suggest that saffron's astragalin and crocin could have inhibitory actions on SARS-CoV-2 protease and spike protein, respectively. CONCLUSION: Saffron represents a promising substance for toning down cytokine storm during COVID-19, as well as a potential preventive treatment for COVID-19. However, appropriate randomized clinical trials, especially those using biomarkers as surrogates to assess inflammatory status, should be designed in order to assess the clinical efficacy of saffron and allow its use as an adjunct treatment modality, particularly in resource-poor settings where access to drugs may be limited.

Saffron (Crocus sativus L.) and health outcomes: a meta-research review of meta-analyses and an evidence mapping study.

BACKGROUND: Although a number of systematic reviews and meta-analyses of saffron (Crocus sativus L.) have been published, no study has comprehensively summarized the clinical evidence from meta-analyses, or assessed the reporting or methodological quality of these reviews. PURPOSE: The present meta-research study was designed to fill the gaps in knowledge to inform future studies and allow enhanced clinical decision-making on saffron. METHODS: The PubMed, Cochrane Library, Embase, and CNKI databases were systematically searched from inception to April 3 rd, 2021, for meta-analyses of clinical trials that assessed the efficacy and safety of saffron. PRISMA 2009 and AMSTAR-2 were employed to assess the reporting and methodological quality of meta-analyses identified in the search, respectively. The present study was registered on PROSPERO with registration number CRD42020220274. RESULTS: Nineteen eligible systematic reviews with meta-analyses published in English were identified from 235 records. These meta-analyses were published in 12 peer-reviewed journals from 2013 to 2021. The heterogeneous results indicated that saffron significantly reduced fasting blood glucose, waist circumference, diastolic blood pressure, concentrations of total cholesterol and low-density lipoprotein cholesterol, and improved symptoms of depression, cognitive function and sexual dysfunction compared with controls (mainly placebos). Common side effects of saffron consumption included nausea, dry mouth, poor appetite, and headache, but no serious adverse reactions were reported. Primary analysis and sensitivity analysis confirmed that the reporting and methodological quality of reviews included in the study were highly correlated (p < 0.001). The quality of meta-analyses of saffron requires improvement by including a structured abstract, a prospective protocol and registration, explanation of the study designs within each study that is reviewed, the searches, risk of bias assessment, literature selection, and reporting of funding sources. CONCLUSION: The available evidence indicates that saffron is a safe plant for administration as a medicine and can improve diverse clinical outcomes, but the scientific quality of the published systematic reviews needs to be improved. Moreover, the clinical effects of saffron need to be confirmed through high-quality randomized trials in multiple countries with large sample sizes.

Effects of mild temperature conditions during dehydration procedures on saffron quality parameters.

BACKGROUND: The dehydration procedure is responsible for saffron sensorial properties: colour, taste and aroma. Changes in the compounds responsible for these characteristics have been studied when dehydration processes at high and low temperature are employed. However, the evolution of these changes at mild temperatures is not available in the current bibliography. In this paper the effect of different mild conditions (18-20 degrees C for 24 h, 40-50 degrees C for 75 min and 55 degrees C for 75 min) applied to 45 saffron samples with the same origin was investigated. RESULTS: Crocetin esters, the compounds responsible for saffron colour, increased their content with no significant differences from other processes when high temperatures (55 degrees C) were used, thus producing a noticeable increment in saffron colouring capability. Similar behaviour was obtained for picrocrocin, the compound responsible for saffron taste, with higher average content at the highest temperature (55 degrees C) but without significant differences with the inferior conditions (40-50 degrees C). However, more volatile compounds were generated, especially safranal,at higher temperatures, e.g. 55 degrees C, during the dehydration procedure. CONCLUSIONS: The results found support the idea for employing mild to high temperatures during the dehydration process of saffron.

Citrus essential oils and four enantiomeric pinenes against Culex pipiens (Diptera: Culicidae).

The aim of this study was to evaluate the toxicity of pinenes (enantiomers of alpha- and beta-) and essential oils from Greek plants of the Rutaceae family against the mosquito larvae of Culex pipiens (Diptera: Culicidae). Essential oils were isolated by hydrodistillation from fruit peel of orange (Citrus sinensis L.), lemon (Citrus limon L.), and bitter orange (Citrus aurantium L.). The chemical composition was determined by gas chromatography/mass spectrometry (GC/MS) analysis. Citrus essential oils contained in high proportion limonene and in lower quantities p-menthane molecules and pinenes. The insecticidal action of these essential oils and enantiomers of their pinenes on mosquito larvae was evaluated. Plant essential oils exhibited strong toxicity against larvae with the LC(50) values ranging from 30.1 (lemon) to 51.5 mg/L (orange) depending on Citrus species and their composition. Finally, the LC(50) value of pinenes ranging from 36.53 to 66.52 mg/L indicated an enantioselective toxicity only for the beta-pinene enantiomer.

Coactivity of sulfide ingredients: a new perspective of the larvicidal activity of garlic essential oil against mosquitoes.

BACKGROUND: The activity of several garlic oil ingredients against Culex pipiens L. larvae was studied. In addition to diallyl sulfide (DS) and diallyl disulfide (DDS), the garlic oils used included one essential oil (EO) and two semi-synthetic garlic essential oils (SSGEO1 and SSGEO2), which resulted from the enrichment of EO with DS and DDS standards respectively. The oils were compared with respect to their toxicity. RESULTS: The chemical composition of the tested oils was evaluated by means of gas chromatography-mass spectrometry. Experimental data from the tested samples revealed high toxicity. In detail, DDS (6.09 mg L(-1)) was the most active, followed by SSGEO2 (7.05 mg L(-1)) and EO (8.01 mg L(-1)), while SSGEO1 and DS were relatively inactive. CONCLUSION: The addition of DDS to EO did not change the toxic effect of the essential oil, whereas the presence of DS in excess produced an enriched essential oil with low toxicity. Furthermore, the antagonistic effect of DS and DDS against the other components of EO was shown by the application of two equations obtained from the literature. Their larvicidal performances were correlated, for the first time, with their detailed chemical composition. Data analysis strongly indicated the toxicity of the other EO sulfur ingredients.

Encapsulation of Mentha pulegium Essential Oil in Yeast Cell Microcarriers: An Approach to Environmentally Friendly Pesticides.

A green approach for the encapsulation of Mentha pulegium essential oil in commercial baker's yeast and its evaluation as a pesticide against the insect pest Myzus persicae are presented. Upon treating aqueous yeast cell dispersion with the essential oil, the formation of essential-oil-loaded microparticles of about 9 µm is observed, with a loading capacity ranging from 29 to 36%, depending upon the encapsulation conditions. The thermal properties of the microparticles were characterized using differential scanning calorimetry and thermogravimetric analysis, confirming the protection of the essential oil from the cells. Encapsulation prolonged the insecticidal activity of the essential oil by 3 days.

DNA interaction with saffron's secondary metabolites safranal, crocetin, and dimethylcrocetin.

Saffron comes from the dried red stigmas of the Crocus sativus L. flower. Except for its use in cooking and in traditional medicine, it has numerous applications as an antitoxic, antioxidant, and anticancer agent due to its secondary metabolites and their derivatives (safranal, crocins, crocetin, dimethylcrocetin). However, there has been no information on the interactions of these secondary metabolites with individual DNA at molecular level. This study was designed to examine the interaction of safranal, crocetin (CRT), and dimethylcrocetin (DMCRT) with calf-thymus DNA in aqueous solution at physiological conditions, using constant DNA concentration (6.25 mM) and various drug/DNA(phosphate) molar ratios from 1/48 to 1/2. FTIR and UV-visible difference spectroscopic methods are used to determine the drug binding sites, the binding constants, and the effects of carotenoids and safranal complexation on the stability and conformation of DNA duplex. Both intercalative and external binding modes were observed, with overall binding constants K(safranal) = 1.24 x 10(3) M(-1), K(CRT) = 6.2 x 10(3) M(-1) and K(DMCRT) = 1.85 x 10(5) M(-1) A partial B- to A-DNA transition occurs at high carotenoids and safranal concentrations.

Effects of the active constituents of Crocus sativus L., crocins on recognition and spatial rats' memory.

Crocus sativus L. is a plant cultivated in various parts of the world. Its involvement in learning and memory processes has been proposed. Crocins are water-soluble carotenoids and are among the active components of C. sativus L. The present study was designed to investigate in the rat the effects of crocins on recognition and spatial memory. For this aim, the object recognition task which evaluates non-spatial working memory and a novel version of the radial water maze which assesses spatial reference and spatial working memory were chosen. In a first study, crocins (15 and 30mg/kg) counteracted delay-dependent recognition memory deficits in the normal rat, suggesting that these carotenoids modulate storage and/or retrieval of information. In a subsequent study, treatment with crocins (30mg/kg and to a lesser extent also 15mg/kg) attenuated scopolamine (0.2mg/kg)-induced performance deficits in the radial water maze test. The present results support and extend the enhancing effects of crocins on memory and, then, to our knowledge, for the first time, demonstrate its implication in the mechanisms underlying recognition and spatial memory.

Interaction of tRNA with Safranal, Crocetin, and Dimethylcrocetin.

Saffron is the red dried stigmas of Crocus sativus L. flowers and used both as a spice and as a drug in traditional therapeutic. The biological activity of saffron in modern medicine is in development. Its numerous applications as an anti-oxidant and anti-cancer agent are due to its secondary metabolites and their derivatives (safranal, crocins, crocetin, dimethylcrocetin). The aim of this study was to examine the interaction of transfer RNA with safranal, crocetin, and dimethylcrocetin in aqueous solution at physiological conditions. Constant tRNA concentration (6.25 mM) and various drug/tRNA (phosphate) molar ratios of 1/48 to 1/8 were used. FT-IR and UV-Visible difference spectroscopic methods have been applied to determine the drug binding mode, the binding constants and the effects of drug complexation on the stability and conformation of tRNA duplex. External binding mode was observed for safranal crocetin and dimethylcrocetin, with overall binding constants K(safranal) = 6.8 (+/- 0.34) x 10(3) M(-1), K(CRT) = 1.4 (+/- 0.31) x 10(4) M(-1), and K(DMCRT) = 3.4 (+/- 0.30) x 10(4) M(-1). Transfer RNA remains in the A-family structure, upon safranal, crocetin and dimethylcrocetin complexation.

Crocetin, dimethylcrocetin, and safranal bind human serum albumin: stability and antioxidative properties.

Crocetin (CRT) and dimethylcrocetin (DMCRT) are derived from crocins which are found in the stigmas of saffron (Crocus sativus L.), while safranal is the main component of saffron's essential oil. The aim of the present study was to examine their interaction with human serum albumin in aqueous solution at physiological conditions using constant protein concentration and various ligand contents. FT-IR and UV-visible spectroscopic methods were used to determine the ligands' binding mode, the binding constant, and the effects of ligand complexation on protein secondary structure. Structural analysis showed that crocetin, dimethylcrocetin, and safranal bind nonspecifically (H-bonding) via protein polar groups with binding constants of Kcrt =2.05 (+/-0.30) x 103 M-1, Kdmcrt = 9.60 (+/-0.35) x 104 M-1, and Ksaf = 2.11 (+/-0.35) x 103 M-1. The protein secondary structure showed no major alterations at low ligand concentrations (1 microM), whereas at higher content (1 mM), decrease of alpha-helix from 55% (free HSA) to 43-45% and increase of beta-sheet from 17% (free HSA) to 18-22% and random coil 7% (free HSA) to 10-14% occurred in the ligand-HSA complexes. The results point to a partial unfolding of protein secondary structure at high ligand content. The antioxidant activity of CRT, DMCRT, and safranal was also tested by the DPPH* antioxidant activity assay, and their IC50 values were compared to that of well-known antioxidants such as Trolox and butylated hydroxy toluene (BHT). The IC50 values of CRT and safranal were 17.8 +/- 1 microg/mL and 95 +/- 1 microg/mL, respectively, while the inhibition of DMCRT reached a point of 38.8%, which corresponds to a concentration of 40 microg/mL, and then started to decrease. The IC50 values of Trolox and BHT were 5.2 +/- 1 microg/mL and 5.3 +/- 1 microg/mL, respectively.

Assessing saffron (Crocus sativus L.) adulteration with plant-derived adulterants by diffuse reflectance infrared Fourier transform spectroscopy coupled with chemometrics.

Saffron, the dried red stigmas of the plant Crocus sativus L., is well-known as one of the most important and expensive spices worldwide. It is thus highly susceptible to fraudulent practices that employ, among others, plant-derived adulterants. This study presents an application of diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and chemometric techniques for evaluating adulteration of saffron with six characteristic adulterants of plant origin, i.e. C. sativus stamens, calendula, safflower, turmeric, buddleja, and gardenia. The proposed method involved a three-step process for the detection of adulteration as well as for the identification and quantification of adulterants. Partial least squares discriminant analysis (PLS-DA) was applied to perform authentication of saffron based on mid-infrared fingerprints (4000-600cm-1), resulting in 99% correct classification of pure saffron and saffron adulterated at 5-20% (w/w) levels. Adulterant identification in positive samples was performed with high sensitivity and specificity by a six-class PLS-DA model, with spectroscopic data from the region 2000-600cm-1. Subsequently, partial least squares (PLS) regression models were built for the quantification of each adulterant. By using synergy interval PLS (siPLS) for variable selection, models with improved performance were developed, with detection limits ranging from 1.0% to 3.1% (w/w). The results obtained illustrate that this strategy based on DRIFTS has the potential to complement existing methodologies for the rapid and cost-effective assessment of typical saffron frauds.

Sudan dyes in adulterated saffron (Crocus sativus L.): Identification and quantification by (1)H NMR.

Saffron, the dried red stigmas of Crocus sativus L., is considered as one of the most expensive spices worldwide, and as such, it is prone to adulteration. This study introduces an NMR-based approach to identify and determine the adulteration of saffron with Sudan I-IV dyes. A complete (1)H and (13)C resonance assignment for Sudan I-IV, achieved by two-dimensional homonuclear and heteronuclear NMR experiments, is reported for the first time. Specific different proton signals for the identification of each Sudan dye in adulterated saffron can be utilised for quantitative (1)H NMR (qHNMR), a well-established method for quantitative analysis. The quantification of Sudan III, as a paradigm, was performed in varying levels (0.14-7.1g/kg) by considering the NMR signal occurring at 8.064ppm. The high linearity, accuracy and rapidity of investigation enable high resolution (1)H NMR spectroscopy to be used for evaluation of saffron adulteration with Sudan dyes.

Comparative evaluation of an ISO 3632 method and an HPLC-DAD method for safranal quantity determination in saffron.

The aim of this work was a comparison of the ISO 3632 (2011) method and an HPLC-DAD method for safranal quantity determination in saffron. Samples from different origins were analysed by UV-vis according to ISO 3632 (2011) and by HPLC-DAD. Both methods were compared, and there was no correlation between the safranal content obtained by UV-vis and HPLC-DAD. An over-estimation in the UV-vis experiment was observed, which was related to the cis-crocetin esters content, as well as other compounds. The results demonstrated that there was no relationship between ISO quality categories and safranal content using HPLC-DAD. Therefore, HPLC-DAD might be preferable to UV-vis for determining the safranal content and the classification of saffron for commercial purposes. In addition, HPLC-DAD was adequate for determining the three foremost parameters that define the quality of saffron (crocetin esters, picrocrocin and safranal); therefore, this approach could be included in the ISO 3632 method (2011).

Interaction of antioxidant flavonoids with tRNA: intercalation or external binding and comparison with flavonoid-DNA adducts.

Antioxidants are essential to good health. Flavonoids are powerful antioxidants, and prevent DNA damage. The antioxidative protections are related to their binding modes to a DNA duplex and complexation with free radicals in vivo. Recently we reported the interaction of flavonoids with DNA in vitro (Kanakis et al., J. Biomol. Struct. Dyn. 22, 719-724, 2005), where polyphenol different binding modes were discussed. The aim of this study was to examine the interaction of transfer RNA with quercetin (que), kaempferol (kae), and delphinidin (del) in aqueous solution at physiological conditions and to make a comparison with the corresponding pigment-DNA adducts. Constant tRNA concentration (6.25 mM) and various drug/RNA(phosphate) molar ratios of 1/48 to 1/8 were used. FTIR and UV-visible difference spectroscopic methods have been applied to determine the drug binding mode, the binding constants, and the effects of drug complexation on the stability and conformation of tRNA duplex. Both intercalative and external binding modes were observed. Structural analysis showed que, kae, and a del intercalate tRNA duplex with minor external binding to the major or minor groove and the backbone phosphate group with overall binding constants K (que) = 4.80 x 10(4) M(1), K (kae) = 4.65 x 10(4) M(1), and K (del) = 9.47 x 10(4) M(1). The stability of adduct formation is in the order of del > que > kae. A comparison with flavonoids-DNA adducts showed both intercalation and external bindings with the stability order K (que) = 7.25 x 10(4) M(1), K (kae) = 3.60 x 10(4) M(1), and K (del) = 1.66 x 10(4) M(1). Low flavonoid concentration induces helical stabilization, whereas high pigment content causes helix opening. A partial Bto A-DNA transition occurs at high drug concentration, while tRNA remains in the A-family structure.

Inhibitory activity on amyloid-beta aggregation and antioxidant properties of Crocus sativus stigmas extract and its crocin constituents.

Crocus sativus stigmas are one of the widely known spices (saffron) and consist of unusually polar carotenoids. Alzheimer's disease is characterized pathologically by deposition of amyloid beta-peptide (Abeta) fibrils. Oxidation is thought to promote Abeta fibril formation and deposition. To identify agents inhibiting the pathogenesis of Alzheimer's disease, we examined in vitro the antioxidant properties of extract of C. sativus stigmas and its effect on Abeta(1-40) fibrillogenesis. The antioxidant properties were determined by measuring the ferric-reducing antioxidant power and Trolox-equivalent antioxidant capacity, while its effects on Abeta-aggregation and fibrillogenesis were studied by thioflavine T-based fluorescence assay and by DNA binding shift assay. The water:methanol (50:50, v/v) extract of C. sativus stigmas possesses good antioxidant properties, higher than those of tomatoes and carrots, and inhibited Abeta fibrillogenesis in a concentration and time-dependent manner. The main carotenoid constituent, trans-crocin-4, the digentibiosyl ester of crocetin, inhibited Abeta fibrillogenesis at lower concentrations than dimethylcrocetin, revealing that the action of the carotenoid is enhanced by the presence of the sugars. Our findings suggest the possible use of C. sativus stigma constituents for inhibition of aggregation and deposition of Abeta in the human brain.